1. Technical Field
This disclosure relates to computer networking More specifically, this disclosure relates to methods and apparatus for optimizing and scaling control plane traffic in carrier Ethernet transport networks.
2. Related Art
Carrier Ethernet is being heralded as the next major innovation in transport and is being sought after in both the enterprise and the service provider worlds. Reliability and availability are key requirements for data services in a transport network. Achieving a reliability value of 99.999% and sub-50 ms restoration is critical for seamless operation of networks. Traditionally, SONET/SDH has been successful in meeting these requirements. Carrier Ethernet technologies are expected to dominate much of transport networks in the future. The primary differentiators between best-effort Ethernet transport and Carrier-class Ethernet transport are the evolution of the data-forwarding plane and the control plane that facilitate managed services. The data-plane relies on service level identifiers that facilitate forwarding of frames in a reliable, deterministic, fault-agnostic, service-differentiated manner. The control plane is responsible for setting up these identifiers (e.g., labels in MPLS-TP, tags in PBB-TE, etc.), configuring network elements, providing and provisioning the protection path and detecting failures.
In a SONET/SDH network, synchronization and overhead bytes within a frame along with the DCC (digital control channel) provides a dedicated failure detection mechanism. In contrast, Carrier Ethernet relies on a specific implementation of the ITU.T1731, ITU.T8031 and IEEE 802.1ag Connectivity Fault Management (CFM) standard that facilitates continuous exchange of heartbeat messages (called Connectivity Check Messages or CCMs) that enable a destination node to isolate service failure. The CFM standard provides for creation of Management End-Points (MEPs) at source and destinations for a particular service. These MEPs continuously communicate by sending CCM heartbeat messages from the source to the destination at periodic intervals.
The CCMs are usually generated per service, and when a destination does not receive three consecutive CCMs, the destination determines that a fault has occurred for the service and initiates a protection mechanism. Since CCMs are generated per service, there is a continuous exchange of CCM heartbeat messages across the network for every service provisioned in the network. This potentially leads to heavy traffic and can reduce the efficiency of the network. The problem of such a control plane is that for every active data-service, the control plane uses a separate, in-band control service that sends a continuous flow of CCMs. The amount of data generated by the control plane can create scalability issues at intermediate nodes, which can adversely impact network growth.
To illustrate the significance of the problem of control plane traffic, consider a network over which 1000 services are to be provisioned. If CCMs are generated per service (in compliance with the CFM standard), the total CCM traffic over the entire network will be about 1 Gbps (two bi-directional CCMs of 64 bytes each per service every 10 ms).